+ Added sequence completion column Added a column to the Scheduler list, with light frame currently captured, and required. These are connected to SchedulerJob attributes. The scheduler fills the current and required capture counts when it estimates the duration of the job, displaying "<current>/<required>" in the new column. Note that several issues make the actual count incorrect in some cases, this will be reworked later on.

+ Enum-defined jobs columns and positions
Used an enum to position jobs columns in the UI. While this eases repositioning
in code, .ui still needs to be updated because column headers are not populated
dynamically (yet). Also removed a useless cell reset in SchedulerJob (will be
reworked later on).

+ Reworked SchedulerJob cell widget management
Improved the shortcuts to update cell widgets in queueTable from
SchedulerJob instances, even if SchedulerJob should only be a data
model. Centralized updates in updateJobCell, but will somehow optimize
it by relocating the code to the relevant functions instead.
Rewriting this also makes it obvious that when a job is scheduled, there's
something weird happening with the startup time.

+ Added score column
Added a widget cell for the score, now displayed in queueTable. Because
negative scores are a bit of an ergonomy issue, those will simply render as
"<0". Basically, negative scores are a no-go for now. Current rework makes a
few issues more obvious, in order to fix them later on.

+ Connected completion time to widget cell
Now completion time will update its widget cell when a job is scheduled to end
at a particular time. This is not very helpful for other states right now, but
also makes it obvious that there are no other states using that column.

FIXME on altitude cutoff, which sometimes cancels a rising target.
FIXME on location of cell updates, either UpdateJobCell or in each setter.
FIXME on resetting a scheduler job when adding it, in the case there is no change.
FIXME on proper "reset" function for scheduler jobs.
FIXME on KNotification on error state from SchedulerJob.
FIXME on special case where estimatedTime is zero, set when job is complete.
FIXME on displaying negative scores.

Differential Revision: https://phabricator.kde.org/D12325